This field of the invention relates generally to industrial combustion systems, and more particularly to methods and systems for removing carbon dioxide (CO2) from pre-combustion syngas before passing to a gas turbine power system.
At least some known carbon separation technologies intervene at different points in coal and/or natural gas systems. For example, carbon separation technologies that separate CO2 from combustion flue gases are generally known as post-combustion carbon separation technologies. Known post-combustion carbon separation technologies include processes, for example, physical absorption, cryogenic separation, solid sorbent separation, chemical looping combustion, chemical absorption, and/or membrane separation. In addition, these carbon technologies can be used to remove CO2 from pre-combustion gasses, such as syngas.
Some known chemical absorption processes attempt to remove CO2 from the flue gases by an exothermic reaction of CO2 with separation solvents, for example, potassium carbonate, sodium hydroxide, amine-based, and ammonia based solvents. During a known chemical absorption process, for example, a flue gas and an ammonia-based liquid counter-currently flow within a scrubber.
The combustion flue gas stream generally includes a smaller volume of CO2 as compared to the larger volume of the flue gas. Known scrubbers generally require equipment sizes capable of processing the larger volumes of flue gas. During processing within known scrubbers, the flue gas is dispersed into the liquid causing gas bubbles to be formed within the liquid. The CO2 absorption amount of the liquid partially depends on a total gas-liquid contact area, which is the sum of the surface areas of the gas bubbles. The liquid may absorb CO2 and other impurities, for example, carbon oxysulfide and carbon bisulfide. Such known impurities may cause foaming of the liquid and/or liquid degradation due to irreversible reactions with the impurities. Also, a driving force that is required to separate the CO2 from the flue gas is determined based on a concentration (density) of flue gas components. The scrubber footprint and stripper regeneration energy increases capital cost, operating costs, and energy consumption. A plant capacity is also reduced because of electrical power consumption in known chemical absorption processes. It would be desirable to provide a method to remove the CO2 before combustion to reduce energy requirements associated with post-combustion removal of CO2.